WO2003040546A1

WO2003040546A1 - Common-ramp-injector

Info

Publication number: WO2003040546A1
Application number: PCT/DE2002/004016
Authority: WO
Inventors: Karl Hofmann
Original assignee: Robert Bosch Gmbh
Priority date: 2001-11-09
Filing date: 2002-10-25
Publication date: 2003-05-15
Also published as: JP2005508477A; US20040041039A1; KR20040054601A; DE10155271A1; EP1446572A1; PL368674A1

Abstract

The invention concerns an injector for high-pressure fuel injection for auto-ignition internal combustion engines, comprising a hollow body (1) provided at one of its ends a valve seat (2) and at least an injection orifice (3). The inventive injector further comprises a needle valve (4) which is arranged in the extension of a valve piston (5) in the injector body (1) and which, when closed, closes at least the injection orifice (3), and at least a spring which maintains the injector closed, when there is no pressure, by pressing the needle valve (4) on the valve seat (2). Said injector comprises at least two magnetic devices for directly opening and closing the injector.

Description

Common rail injector

Technical field

The common rail injection system is used to inject fuel into direct-injection ner internal combustion engines. In this accumulator injection system, pressure generation and injection are decoupled from one another in time and place. A separate high-pressure pump generates the injection pressure in a central high-pressure fuel reservoir. The start of injection and the injection quantity are determined by the triggering time and duration of, for example, electrically operated injectors which are connected to the high-pressure fuel reservoir via fuel lines.

State of the art

DE 196 50 865 AI relates to a solenoid valve for actuating a common rail injector. Such an injector is shown in FIG. 1 of this published specification. The injector is directly connected to a high-pressure fuel reservoir (common rail), which is constantly supplied with fuel under high pressure by a high-pressure feed pump. The high-pressure fuel is supplied to the combustion chamber of the internal combustion engine via the solenoid valve-controlled injector.

An injection by means of an injector according to FIG. 1 of DE 196 50 865 AI proceeds as follows; The opening and closing of the valve needle is controlled by the solenoid valve. In the de-energized state of the electric solenoid valve, an outlet throttle (A throttle), via which the valve control chamber is connected to the fuel return, is closed by the valve member. The high pressure that is also present in the high-pressure fuel accumulator can then build up very quickly in the valve control chamber via an inlet throttle (Z throttle). The pressure in the valve control chamber, together with a return spring, generates a closing force on the valve needle that is greater than the forces acting on the valve needle in the opening direction as a result of the high pressure. If the valve control chamber is opened towards the relief side by opening the solenoid valve, the pressure in the small volume of the valve control chamber decreases very quickly, since it is decoupled from the high pressure side via the A throttle. As a result, the force acting on the valve needle in the opening direction outweighs the high fuel pressure applied to the valve needle, so that it moves upward and thereby Injection openings are opened for injection. This indirect control of the valve needle via a hydraulic booster system is used because the forces required to open the valve needle quickly cannot be generated directly with the solenoid valve. The so-called control amount required in addition to the injected fuel amount reaches the fuel return via the throttle of the valve control chamber.

The injection quantity in this common rail system used in the prior art is determined by the control of the solenoid valve, the coordination of the Z and A throttle and the geometries of the valve piston and the valve needle. The number of components required makes the system expensive. Furthermore, the injection quantity is subject to a large spread due to the influence of the individual parameters and tolerances.

Presentation of the invention

The solution according to the invention has the advantage that components can be saved in the common rail injector, so that the costs are reduced. Furthermore, the number of influencing parameters on the injection quantity is reduced and the injection quantity is controlled more precisely. According to the invention, these advantages are achieved by an injector for the high-pressure injection of fuel in self-igniting internal combustion engines, the injector containing a hollow injector body which comprises at one end a valve seat and at least one injection opening. Furthermore, the injector according to the invention comprises a valve needle which is arranged in the extension to a valve piston in the injector body, so that it closes the at least one injection opening in the closed state and at least one spring which closes the injector in the depressurized state by pressing the valve needle into the valve seat holds. Furthermore, the injector according to the invention contains at least two magnetic devices which serve for the direct opening and closing of the injector.

The effort for at least two magnetic devices for direct control is significantly less than for indirect control of the valve needle via a hydraulic booster system with A and Z throttle. For the direct actuation of the valve needle, forces are required which, given the dimensions of the injector, cannot be applied by a magnetic device alone. Therefore, the injector according to the invention comprises at least two magnetic devices, which together can exert sufficiently large forces to open the valve needle. drawing

The present invention is explained in more detail below with reference to the drawing.

It shows:

FIG. 1 shows a schematic illustration of an injector according to the invention with two magnetic devices,

FIG. 2 shows a first embodiment of a valve needle tip according to the invention,

FIG. 3 shows a diagram with the magnetic force as a function of the air gap between the electromagnet and the magnet armature,

FIG. 4 shows a second embodiment of a valve needle tip according to the invention with a throttle gap and

FIG. 5 shows a third and fourth embodiment of a valve needle tip according to the invention with a throttle gap.

variants

FIG. 1 shows an injector according to the invention with two magnetic devices 37, 38. The injector consists of a hollow projector body 1 which contains a valve seat 2 and several injection openings 3 at one end. A valve needle 4 is arranged in an extension to a valve piston 5 in the injector body 1. The valve needle 4 closes the injection openings 3 tightly against the combustion chamber (not shown) in the closed state of the injector. In this state, there is therefore no injection of fuel into the combustion chamber of the internal combustion engine.

In the left half of the injector illustrated is a variant with two springs 6, 7 in the right half of a variant with a spring 8. The springs 7 and 8 If it is pressure springs which pressure-less injector in ^' Keep condition closed. They can also be used to ensure the closing process of the open injector at the end of an injection. The springs 6, 7, 8 are located in a spring chamber 9 contained in the injector body 1. The inner spring 7 (in the case of two springs) and the spring 8 (in the case of one spring) rest at one end on a wall of the spring chamber 10. At their other end they encounter a disc 11 which is connected to the valve piston 5 connected is. When the injector is open, the valve piston 5, including the disk 11, is pushed into the spring chamber 9 in the opening direction 12, so that the spring 7, 8 is compressed and thus exerts a force in the closing direction 13 on the disk 11 and the valve piston 5.

In the variant with two springs 6, 7, the outer spring 6 also abuts with one end on the wall of the spring chamber 10, where it is fastened. At the other end, the spring 6 is connected to an annular disk 14, which is supported on the injector body 1. The outer spring 6 is biased to a defined force. The underside of the ring-shaped disc 14 is at a distance 15 from the top of the disc 11. If the valve needle 4 with the valve piston 5 and the disc 11 is moved by the distance 15 in the opening direction 12 when the injector is opened, the ring-shaped disc lies 14 on the disc 11. When the injector is opened even further as a distance 15, the disk 11 and the annular disk 14 are moved together in the opening direction 12 in the spring chamber 9, so that both springs 6, 7 are compressed at the same time and exert a force on the valve piston 5 in the closing direction 13 ,

In the preferred embodiment of the present invention shown in FIG. 1, a high-pressure line 21 runs in the center in the longitudinal direction in the injector, through which the fuel under high pressure flows from a high-pressure fuel reservoir (not shown) into the injector Injector leads to a fuel reservoir 22 of the injector. The fuel under high pressure passes through an inlet 23 into the high pressure line 21. This opens into the spring chamber 9 (through the wall 10) and is continued on the other side of the spring chamber 9 through the disk 11 and the valve piston 5. In the area of the fuel supply chamber 22, the valve piston 5 has a plurality of openings 24 through which the fuel reaches the fuel supply chamber 22. From there, the fuel can flow along the valve needle 4 to the injection openings 3. A leakage line 27 serves to drain leakage quantities of the fuel.

In this preferred embodiment of the present invention, two magnetic devices 37, 38, which each contain a magnet armature 16, 17 and an electromagnet 18, 19, serve to directly open and close the injector. The electromagnets 18, 19 are firmly connected to the injector body 1. The electromagnets 18, 19 are connected in parallel via an electrical current connection 25 to a current source (not shown).

In the preferred embodiment of the present invention shown in FIG. 1, the magnet armatures 16, 17 have a different stroke (hi or h ₂ ). Under the hub (hi, h ₂ ) is to be understood as the path that the armature 16, 17 travels in the opening direction when the injector is opened until it bears against the associated electromagnet 18, 19. FIG. 1 shows an injector according to the invention in which the stroke hi of the first magnet armature 16 is smaller than the stroke h _{2 of} the second magnet armature 17. The stroke hi of the first magnet armature is preferably 30-60 μm and the stroke h _{2 of} the second magnet armature 150 250 μm.

In this preferred embodiment of the present invention, the second armature 17 is fixed on the valve piston 5. Furthermore, the first magnet armature 16 is slidably arranged on the valve piston. When the injector is closed, the first magnet armature 16 is located at an upper stop 20, which is created by an annular bulge in the valve piston 5. In this position of the first magnet armature 16, it is non-positively connected to the valve piston 5, which has a diameter di. When the injector is closed, the first magnet armature 16 is held on the upper stop 20 by a return spring 39. When the electromagnets 18, 19 are energized, the magnetic force of the first electromagnet 18 acts on the first magnet armature 16 in the opening direction 12. At the same time, the magnetic force of the second electromagnet 19 acts on the second magnet armature 17 in the opening direction 12. The magnetic force of the two electromagnets 18 , 19, the magnet armatures 16, 17 move the valve piston 5 with the valve needle 4 in the opening direction 12, since the second magnet armature 17 is fixed and the first magnet armature 16 is connected to the valve piston 5 via the upper stop 20. The valve needle 4 consequently lifts off the valve seat 2 and the fuel under high pressure is injected via the injection openings 3.

Due to its smaller stroke hi, the first magnet armature 16 bears against its associated first electromagnet 18 before the second magnet armature 17 during an opening operation of the injector. However, since the first magnet armature 16 is slidably arranged on the valve piston 5, the second magnet armature 17, including the valve piston 5 firmly connected thereto, can move further in the opening direction 12 until the second magnet armature 17 also abuts its associated second electromagnet 19. The first magnet armature 16 slides over a part 26 of the valve piston 5, which has a smaller diameter than the valve piston 5 at the upper stop 20. When the injector is closed, the first magnet armature returns to its starting position at the upper one with the aid of the return spring 39 Tee off 20.

The two different strokes hi, h _{2 of} the magnet armatures 16, 17 offer the advantageous possibility of stopping the stroke, ie the small stroke hi of the first magnet armature 16 can be started for small injection quantities. So that the movement of the Valve needle 4, which in the prior art has a ballistic course in the load area, is held stably on a partial stroke (hi). As a result, the injection quantity spread is advantageously reduced. The control of the partial stroke hi is possible via the current intensity and / or via the assignment of the distance 15. The partial stroke _\ is set as precisely as possible in terms of production technology, for. B. by moving the electromagnet 18 with subsequent fixing by laser welding.

The injector shown in FIG. 1 is only one possible embodiment of the present invention. It is also conceivable, for example, that an injector according to the invention contains two magnet devices 37, 38, which comprise two magnet armatures fixed to the valve piston with the same stroke h. When the two electromagnets are energized, the valve needle is moved by the stroke h in the opening direction by the magnetic force acting on the magnet armature.

It is also conceivable, for example, to energize the individual electromagnets via separate electrical connections, as a result of which the magnetic force on the magnet armatures 16, 17 can be varied more freely.

In the preferred embodiment of the present invention shown in FIG. 1, the diameter di of the valve piston 5 (in the opening direction 12 relative to the upper stop 20) is equal to the diameter d _{2 of} the valve piston 5 (in the closing direction 13 relative to the second magnet armature 17). When the injector is open, there is an equilibrium of the forces from the high pressure in the opening and closing directions (12, 13), since the effective areas to which the high pressure exerts a force in these two directions (12, 13) are the cross-sectional areas of the valve piston 5 with diameters di and d are ₂ . When the injector is open, the force of the high pressure acts in the closing direction 13 on a surface

and in the opening direction 12 onto a surface

With the same diameter di = d _{2, the} following therefore applies (with the injector open) A o ofifiecnn. _ _A open _ A _Λ. o ° ffen

and thus

open . _Λ open _ - open

^: P

where p stands for high pressure. To close the injector after switching off the electromagnets 18, 19, an additional force is therefore required, which is applied by the springs 6, 7, 8.

In the closed state of the injector, the force from the high pressure on the valve piston 5 in the closing direction 13 is preferably greater than the force from the high pressure in the opening direction 12. This is ensured in the embodiment of the present invention shown in FIG. 1 with di = d, since the effective area, on which the high pressure exerts a force in the opening direction 12 on the valve needle 4 and the valve piston 5, is reduced by the valve seat surface 28 (As) when the injector is closed. The force in the closing direction 13 F _! ^ ^301110836 "is therefore greater than the force in the opening ^direction 12

^ closed _{^ Eg} ^

closed d.

Ai - 7t

and

A ₂ closed _ π Λ - A,

\ ^ J

from which follows for dj = d ₂ :

_Λ closed _ _Λ closed _\ A - Ai - As

and thus A ₂ ^closed <Aι ^closed and F ₂ ^closed < ^Fj ^closed .

The closed injector therefore remains closed by the high pressure alone. The force required to open the injector is determined by the area difference Aι ^closed - A ₂ ^closed and the force required to compress the springs 7, 8.

In a further embodiment (not shown) of the present invention, the diameter is di <d ₂ , but the area difference A ₂ ° ^en - Aι o ° ffe ^e n ^{n is} smaller or is at most equal to the valve seat area As. In this embodiment of the present invention as well, the condition A ₂ ° ^f - Aι ° ^ffen <A _s ensures that, when the injector is closed, the force F ^ ⁶³⁰¹¹ ' ⁰³³⁶¹¹ on the valve piston 5 and the valve needle 4 in the closing direction 13 is greater than or equal to Force F _{2 is} ^closed by the high pressure in the opening direction 12.

To close the open injector, the springs 6, 7, 8 in the variant di <d _{2 must have} an additional force ΔF compared to the variant di = d ₂

are applied that are proportional to the area difference

ΔA = A ₂ ^open - A _] ^open

is.

FIG. 2 shows an embodiment of a valve needle according to the invention. This is a valve needle 4, which has a shape corresponding to the prior art, but has a smaller diameter d in the region which, when the injector is closed, bears against the injector body 1 in the valve seat region 31. The smaller diameter d is necessary so that the injector can be opened by the maximum possible magnetic forces from the electromagnets 18, 19. For example, the diameter d can be 1.1 mm in the present invention.

Figure 3 shows a diagram with the magnetic force as a function of the air gap between the electromagnet and the magnet armature. The larger the air gap h between the electromagnet 18, 19 and the magnet armature 16, 17, the smaller the magnetic force F. When the injector is closed, the valve needle tip bears against the valve seat area 31 and the air gap between the second electromagnet 19 and the second magnet armature 17 assumes its maximum size (for example 0.25 mm). At this air gap size 1, the second magnet armature 17 is attracted by the second electromagnet 19 with the magnetic force B. In the partial stroke hi, the air gap size is smaller (air gap size 2) and the second magnet armature 17 is attracted by the larger magnetic field force A. The magnetic force between the first magnet armature 17 and the first electromagnet 19 behaves in the same way. FIG. 4 shows a preferred embodiment of the valve needle according to the invention. In order to reduce the spring force required to close the open injector, in particular in the variant di <d ₂ , the valve needle 4 or the valve needle tip 29 is shaped such that a throttle gap 30 is located between the valve needle 4 and the injector body 1. During the injection process, the pressure in the valve seat area 31 is reduced by the throttle gap 30 and the closing process is thus supported.

FIG. 5 shows two further preferred embodiments of a valve needle according to the invention, one in the left half and another in the right half of the figure. In the two embodiments shown, the valve needle 4 is in turn shaped such that when the injector is open, there is a throttle gap 30 between the valve needle 4 and the injector body 1, which reduces the pressure in the valve seat region 31. The throttling in these embodiments is increased compared to the embodiment shown in FIG. 4, since the throttle gap 30 extends not only in the conical valve seat region 31, but along part of the cylindrical bore 33 in the valve body 1. In the embodiment shown in the right half of FIG. 5, this throttle gap 30 is created along a part of the cylindrical bore 33 of the valve body 1 through a portion 32 of the valve needle 4 in which the valve needle 4 has a larger diameter. As a result, the space between the valve needle 4 and the valve body 1 is reduced, so that a throttle gap 30 is likewise arranged along this partial region 32. This throttle gap 30 remains along the portion 32 regardless of the stroke of the valve needle 4.

In contrast to this, in the preferred embodiment of the injector according to the invention shown in the left half of FIG. 5, the existence or the length of the throttle gap along the partial region 34 depends on the position of the valve needle 4. The further the valve needle 4 in the opening direction 12 relative to the valve body 1 is displaced, the lneinein is the overlap 35 between an area 36 of the bore 33 with a smaller diameter and the portion 34 of the valve needle 4 with a larger diameter. From a stroke of the valve needle 4 which is dependent on the width and arrangement of the regions 34 and 36, there is no longer an overlap 35 and the distance between the valve body 1 and the valve needle 1 increases, so that throttling no longer takes place.

This preferred embodiment of the injector according to the invention shown in the left half of FIG. 5 can advantageously be combined with the embodiment with two springs. When opening the injector, only the longer spring counteracts the magnetic forces. From a certain forward stroke of the longer spring (corresponding to distance 15 in FIG. 1), both springs counteract the opening of the injector. The fairy- However, the forces can be overcome since the high pressure already acts on the valve needle 4 in the seating area when the injector is partially open and the magnetic forces have already risen due to the smaller distance of the respective magnet armature 16, 17 from its electromagnet 18, 19. The injector opens completely and the fuel is injected. The electromagnets are switched off to close. First, both springs 6, 7 act on the valve piston 5. When the shorter spring 6 with the annular disk 14 reaches its stop in the injector body 1 and the longer spring acts solely on the valve piston in the closing direction, the overlap 35 already takes effect and the hydraulic forces (Pressure drop in the valve seat area 31) support the complete closing of the injector.

Claims

claims

1. Injector for high-pressure injection of fuel in self-igniting internal combustion engines

a) a hollow injector body (1) which comprises at one end a valve seat (2) and at least one injection opening (3),

b) a valve needle (4), which is arranged in the extension to a valve piston (5) in the injector body (1), so that it closes the at least one injection opening (3) in the closed state and

c) at least one spring which keeps the injector closed in the depressurized state by pressing the valve needle (4) into the valve seat (2),

characterized in that

the injector comprises at least two magnetic devices (37, 38) that are used for direct

Serve opening and closing the injector.

2. Injector according to claim 1, characterized in that the at least two magnet devices (37, 38) each contain a magnet armature (16, 17) and an electromagnet (18, 19).

3. Injector according to claim 2, characterized in that at least one magnet armature (17) is arranged fixedly on the valve piston (5).

4. Injector according to claim 2, characterized in that at least one magnet armature (16) is slidably arranged on the valve piston (5).

5. Injector according to claim 2, characterized in that the magnet armatures (16, 17) have a different stroke (hi, h ₂ ).

6. Injector according to claim 1, characterized in that a high pressure line (21) runs centrally in the injector in the longitudinal direction, which the fuel under high pressure, which flows from a high-pressure fuel reservoir into the injector, leads through the injector to a fuel on-space (22) of the injector.

7. Injector according to claim 1, characterized in that when the injector is closed, the force F ₁ ^{sch, 033en} by the high pressure on the valve piston (5) and the valve needle (4) in the closing direction (13) is greater than the force F ₂ ^{gescl , Iossen} by the high pressure in the opening ^direction (12).

8. Injelctor according to claim 1, characterized in that when the injector is closed, the force F ^ ^650111033611 by the high pressure on the valve piston (5) and the valve needle (4) in the closing direction (13) is equal to the force F ₂ ^closed by the high pressure in the opening direction (12) is.

9. hijector according to claim 1, characterized gekemizeiclmet that the injector comprises two springs (6, 7), one spring (6) surrounding the other spring (7) and one of the springs (6) is shorter and biased so that it only exerts a force on the valve piston (5) in the closing direction (13) from a certain compression of the longer spring (7).

10. Injector according to claim 1, characterized in that the valve needle (4), in particular its valve needle tip (29), is shaped such that a throttle gap (30) between the valve needle (4) and the injector body (partially open injector) 1) is located.

11. Injector according to claim 10, characterized in that the existence, the size and the length of the throttle gap (30) depend on the position of the valve needle (4).

12. Injelctor according to claim 9, characterized in that an overlap (35) is effective, through which there is a throttle gap (30) between the valve needle (4) and the injector body (1) as soon as the shorter spring (6) stops has reached and the longer spring (7) acts only in the closing direction (13) on the valve piston (5).